Human Anatomy - Kotsan I. Ya. 2009

General overview of the muscles responsible for movements of individual body parts
Movements of the upper limb
Movements of the pectoral girdle

Schematically, the Movements of the Pectoral Girdle (scapula and clavicle) are divided into:

— forward and backward movement with abduction of the scapula from the spine and adduction toward it;

— elevation and depression of the scapula and clavicle;

— Rotation of the scapula around the sagittal axis via its inferior angle in medial and lateral directions;

— circumduction of the lateral end of the clavicle along with the scapula.

Forward movement of the pectoral girdle is performed by Muscles that cross the vertical axis of the sternoclavicular joint and are located anterior to it.

These include:

1) the pectoralis major Muscle, which acts on the pectoral girdle via the humerus;

2) the pectoralis minor muscle;

3) the serratus anterior muscle.

Backward movement of the pectoral girdle is performed by muscles that cross the vertical axis of the sternoclavicular joint and lie posterior to it. These muscles are:

1) the trapezius;

2) the rhomboid Major and minor;

3) the latissimus dorsi (via the humerus).

Elevation of the pectoral girdle is performed by muscles that cross the sagittal axis of the sternoclavicular joint and lie lateral to this axis. They run downward toward the scapula and clavicle. This group of muscles includes:

1) the upper fibers of the trapezius muscle;

2) the levator scapulae muscle;

3) the rhomboid muscles;

4) the sternocleidomastoid muscles.

Depression of the pectoral girdle occurs when the muscles that elevate the pectoral girdle relax, driven by the force of gravity of both the girdle itself and the entire free upper limb. Depression is facilitated by:

1) the pectoralis minor muscle;

2) the subclavius muscle;

3) the lower fibers of the trapezius muscle;

4) the lower slips of the serratus anterior muscle.

In addition, depression is assisted by muscles extending from the trunk to the arm, specifically: the pectoralis major and the latissimus dorsi, primarily through their lower portions.

Internal rotation of the scapula (movement of the inferior angle toward the spine) is produced by a force couple formed by:

1) the pectoralis minor muscle;

2) the lower part of the rhomboid major muscle.

External rotation of the scapula (moving the inferior angle away from the spinal Column laterally) occurs As a result of a force couple formed by the upper and lower PARTS OF THE trapezius muscle. This movement is assisted by:

1) the serratus anterior muscle via its lower and middle digitations;

2) the teres major muscle when the free upper limb is fixed.

Circumduction of the shoulder girdle occurs as a result of the sequential contraction of all its muscles.